On of the largest shells of its type, it can almost completely contain the animal. The shell is oval with a completely sunken point (spire). The shell is variable, but is usually mottled with light yellow-brown blotches and zigzags.

Lives in a wide range of habitats, from seagrass to open coastal tide pools. Found from the mid intertidal to 7m, but greatest numbers are below low tide.

It feed primarily on filamentous green algae, but sometimes will also eat Ulva. It also appears to scrape the diatomaceous film off the leaves of sea-grasses.

The spawn is very recognisable. It consists of an ovoid blob filled with jelly-like mucus in which the eggs are arranged in a spiral string. The eggs are an orange-red colour.

NZ Coastal Marine Inverts. Vol 1 http://www.seaslugforum.net/find/bullquoy accessed 17/ 02/14